The first thing I would suggest you do is get an independent roofer in to look at the flat roof and confirm you don't have a tear (I know you say you had this looked at in March but you need to be sure nothing has happened since then). Your next step, if you really aren't getting anywhere, is undoubtedly to put your position in writing and give the company a deadline for a response. Your original post basically sets out what you need to say, but you should formalise and fill in details such as dates etc. What you need to cover is:
- You contacted company on [date] regarding a new polycarbonate roof.
- Manager came out on [date] and took measurements.
- Roof was manufactured according to those measurements.
- You paid [amount] on [date], on the understanding that the roof would be supplied and fitted to a satisfactory standard.
- Roof was installed on [date]. Clear from the outset that the measurements were incorrect but instead of having the panels re-made the company did [explain bodge job].
- Since installation, you have been plagued by leaks. Company has been to repair no less than [7] times, on [dates if you have a record - even rough dates (e.g. month and year) will do].
- Despite this, you still have a leak which is causing increasing damage to your property. This is unacceptable.
- They are legally obliged to rectify the problem - which extends to dealing with the leak and compensating you for consequent damage to your property.
- You have been very patient but given the ongoing failure by them to repair, you are now considering your legal rights and would like to give them one final chance to make good the roof before you take matters further.
- Ask for a formal response within [14] days, failing which you will no option other than to take matters further.
Will that do you? One option open to you before taking the step of issuing a claim is to get another company in to sort it out and then sue for the cost of doing so. If the leaks could really cause you some damage that might be the cheapest and best way of getting this sorted out. Good luck with it!